The preparation of drugs requires that the drugs be sterile. There are a variety of techniques employed for sterilization, including heat, chemicals, such as ethylene oxide, radiation, and the like. One of the most common techniques is the use of heat, particularly steam heat, referred to as autoclaving. In many cases, the drugs are sterilized as liquid formulations. In order for the formulation to be acceptable, it must fulfill a variety of functions.
One of the criteria for many drugs is that the formulation be at an acceptable physiological pH. For some types of drugs, the osmolality of the solution may be significant. In other situations, there may be concern with the particular inorganic cations present, their concentration, and the like. The cations may have pharmacologic effects, for example affecting the stability of the drug, or its physiological acceptability. Thus, in preparing a drug formulation, a number of factors must be considered, not only as to the physiological effect of the components of the drug formulation, but the interaction of the various components, one upon the other, as well as the effect of heat on such interaction and the individual stability of the components.
For non-ionic contract media there are a number of problems associated with intravascular administration by needle or catheter. The hydrophobicity of the contrast media in conjunction with the amino based buffers employed result in clotting. Furthermore, the absence of sodium ions in the medium results in depression of heart function during coronary angiography.